Mandrel bar steadier



*- "zaand- Feb. 20, 1962 w. scHUETz 3,021,736

MANDREL BAR STEADIER Filed Dec. 6, 1957 4 Sheets-Sheet 1 INVENTOR. `734/455 l/V- SCH U67' Z ATTORNEYS Feb. zo, 1962 J. W. SCHUETZ 3,021,736

MANDREL BAR STEADIER Filed Dec. 6, 1957 4 Sheets-Sheet 2 791% VQ i 42 4 43 30 u |||I|| I||I 46 lo 38 l5' .57 fly-3 la SHA F7' f?- 4 BYnuml( MMQ y l HvA/5413,; ww

l ATTOF/Vf'ys Feb. 20, 1962 J. w. scHUETz MANDREL BAR STEADIER 4 Sheets-Sheet 3 Filed Dec. 6, 1957 INVENTOR. JAMES WSC/0F72 BYZ; Q l s;

4 Sheets-Sheet 4 Filed Deo. 6, 1957 BOTTOM TOF' POL L INVENTOR. `TfV/VES W- SCHUE'Z. Ewa-marnix,

United dtates Patent 3,921,736 MANDREL BAR STEADIER James W. Schuetz, Pittsburgh, Pat, assigner, by mesne assignments, to Blauw-Knox Company, Pittsburgh, Pa., a corporation of Delaware Filed Dec. 6, 1957, Ser. No. 761,254 Claims. (Cl. Sil-13) This invention relates to the manufacture of seamless tubing and more particularly to an improved mandrel bar steadier for piercing mills.

In the manufacture of seamless tubing, one of the initial operations is the piercing of a solid hot cylindrical billet by the action of a pair of angularly disposed driven rolls which cause the billet to feed over a piercing point supported upon the end of a mandrel bar. The billet is rotated by the mill rolls as it is forced over the ercing point, and it is, accordingly, necessary to support the piercing point and mandrel bar for rotation. The mandrel bar extends away from the mill rolls in the direction of longitudinal movement of the billet over the piercing point for a distance that must be at least as great as the length of the longest tube to be formed on the mill. The rear end of the mandrel bar is rotatably supported by a suitable carriage or traveler whereby the bar may be withdrawn or retracted from the tube so that the tube can be removed from the outlet table on which the pierced billet is received. After one pierced billet has been removed, the mandrel bar is then returned to working position with the piercing point adjacent the mill rolls.

inasmuch as modern piercing mills are adapted to Vhandle billets which, when pierced, produce tubes or shells as long as 50 feet, having diameters ranging from .3 or 4 inches to 18 inches or more, it will be understood that the mandrel bar, which carries the piercing point for a large diameter and relatively long ,tube blank, must be very long and heavy. A high compressive load is exerted on the rotary mandrel bar during the piercing operation, and in order to support the bar and prevent the bar from buckling and vibrating under the load as it Vis rotated during the piercing operation, the bar must be supported by some type of bar steadier. Similar types of mandrel bar steadying devices are also required in other machines used in the seamless ,tube making process. Therefore, While the present invention :finds its most important use in connection with piercing mills, it is to be understood that where reference is made in this specification and the appended claims to seamless tube mills, it is intended to include not only piercingy mills but also other equipment in which a rotating mandrel bar must be supported under compression within a tube.

A general object of the present invention is the provision of an improved mandrel Vbar steadier for seamless tube mills or the like whereby mandrel bars can be accurately held in a desired position with respect to the billet being pierced 'and supported during the piercing operation so that the operation can be carried out without substantial buckling or vibration of the mandrel bar.

Other objects of the invention include the provision of a mandrel bar steadier having rollers vthat engage the mandrel 'oar which can be adjusted for mandrels ot various sizes without the necessity of changing the rollers; the provision of a mandrel bar steadier having rollers that vengage the mandrel bar in which Vthe rollers can be of relatively large diameter so as to increase the life thereof; the provision of a mandrel bar steadier, having rollers that engage the mandrel bar, which embodies `a sturdy, simple and trouble-free mechanism for actuating the rollers and holding them in yengagement with the mandrel bar; the provision of a mandrel bar steadier having rollers that engage the mandrel bar, in which ice and the provision of a mandrel bar steadier, having rollers that engage the mandrel bar, which can be adpated readily to the outlet tables of both existing and new piercing mills, and which can be removed readily for maintenance Without disturbing any other part of the outlet table, i

Other objects and advantages of the invention will appear from the following description of a preferred form thereof, reference being made to the accompanying drawings in which:

FIGURE l is a plan view of a piercing mill outlet table having mandrel bar steadiers embodying the Vpresent inf vention and somewhat diagrammatically illustrating the piercing mill rolls and the mandrel carriage for advancing and retracting the mandrel bar;

FIGURE 2 is an elevation of the apparatus shown in FIGURE 1;

.FIGURE 3 is a top plan View of one of the mandrel bar steadiers embodying the invention on an enlarged scale, the View being taken as indicated by line 3 3 of FIGURE 2;

:FIGURE 4 is a vertical section ythrough the l,mandrel bar steadier taken as indicated by line 4,-4 of lFIG- URE 3;

FIGURE 5 is a side elevation of the mandrel bar steadier taken as indicated by line S-S of FIGURE ,4;

FIGURE 6 is another side elevation of the mandrel barr steadier showing the opposite side thereof and taken yas indicated by line 6 6 of FIGURE 4; and

FIGURE 7 is a simplied diagram of the hydraulic and electrical controls for the mandrel bar steadier unit.

Referring now to FlGURES 1 and 2 of 'the drawings, mandrel bar steadiers of the present invention are shown in conjunction with a piercing mill having piercing rolls lll and ll which are driven by shafts l2 and 13, respectively, and rotate in the same direction. These rolls engage a billet. 114 that is fed to the pass of the -rolls 10 and 11 by any conventional type of inlet table (not shown). The rolls rotate the billet; and because the axes or" the rolls are angularly related to each other as shown in FIGURE 2', they distort the metal of the billet 14 and advance it over a piercing point 16, which is supported by a mandrel bar 17 The tubular shell Vformed by the piercing operation is advanced in the direction of the arrow in FIGURES l, 2, 3, 5 and 6 and is received by an outlet table indicated in general at A18.

The mandrel bar 17 extends for the lenvth of the outlet table and is supported at its end remote from the piercing point 16 by a mandrel carriage indicated somewhat diagrammatically at Ztl. Mandrel carriage V2d rotatably supports the rear end vof mandrel bar 17, and is varranged to be retracted from the outlet table at the conclusion ot' a piercing operation to Withdraw the mandrel bar vrfrom the pierced shell so that the shell can be removed from the outlet table. After the pierced shell has been removed from the outlet table, the mandrel carriage is returned to the position shown in 'FIGURES l and 2 (so that it is ready for another piercing operation), and the cycle is repeated.

The outlet table embodies an inverted, overlying or hold-down guide ltrough 2l hingedly supported adjacent the mill rolls and adapted to be raised by means cfa suitable linkage and hydraulic cylinder 22 to permit re,- rnoval of a pierced shell. The outlet ktable also embodies a series of longitudinally spaced, upwardly opening, U-shaped guide troughs or supports 23 and a series of underlying, `longitudinally spaced supporting Arollers f2.4, which are mounted on Vaxes transverse `to the axis of tglre mandrel barand can be raised by a hydraulic CylltdIJZS acting through longitudinal connecting rod 26 and bell cranks 27 into position to support the mandrel bar as it is being advanced toward piercing position and retracted therefrom. The outlet table 18 also embodies a plurality of discharge arms 29 ixedly carried by a shaft 30, and normally disposed beneath the level of a shell that has been pierced on the apparatus. After the piercing operation has been completed and the mandrel bar withdrawn from the shell, the shaft 30 is rotated by any appropriate means, such as a hydraulic cylinder and appropriate linkage (not shown) to raise the discharge arms 29 and lift the pierced shell out of the outlet table to a position where it can be readily lifted by a crane or permitted to roll down the arms into a suitable discharge apparatus.

All of the parts heretofore described may be of conventional or Well-known construction and per se form no part of the present invention.

As explained above, the long and heavy mandrel bar is rotated rapidly during operation of the mill and must therefore be supported so as to preclude excessive vibration, which would cause inaccuracies in the pierced shell during the piercing operation and damage the mandrel bar and/or other parts of the mechanism. The present invention relates particularly to the mandrel bar steadiers or supports which engage the mandrel bar at spaced points along its length and support and hold it accurately in position. In the embodiment shown in the drawings, the outlet table 18 is provided with two mandrel bar steadiers indicated at 31 and 32, FIGURES 1 and 2. The mandrel bar steadier 31 is mounted adjacent the holddown guide 21, and steadier 32 is mounted between two of the guide troughs 23. It is evident that for longer outlet tables, more than two steadiers may be employed; while for a very short table, perhaps only one steadier would be necessary. inasmuch as the steadiers are preferably substantially identical in construction, only steadier 32 will be described herein. This is illustrated particu larly in FIGURES 3, 4, and 6. Y

As shown in these iigures, a mandrel bar steadier made according to the present invention comprises three bar engaging rollers 35, 36 and 37. The rollers 35, 36 and 37 are adapted to engage the mandrel bar 17 in spaced zones around its circumference to rotatably hold it in its desired position. The rollers are also arranged to be withdrawn, at Will, from engagement with the mandrel bar to a position to permit the pierced shell to pass through the steadier as it is formed and also to permit the completed shell to be removed from the apparatus by the arms 29. In order to support the rollers 35, 36 and 37, a pair of massive, transversely extending supporting members or brackets 38 and 39 are mounted on Y the longitudinally extending base members 41 and 42 of the outlet table 18 as by bolts 43 and 44, see FIG- URES 3 and 6. As shown in FIGURES 3 and 4, brackets 38 and 39 have a transversely extending base portion 46 which rests on the longitudinally extending members 41 and 42. At one end of the base portions 46 of the brackets there are aligned openings that receive trunnions 48 (see FIGURES 3 and 4) which pivotally support the lower roller supporting arm 49. Arm 49 includes longitudinally spaced, transversely extending parallel side members S0 which carry the trunnions 4S at one end, the roller 37 intermediate the ends and are curved upwardly, as shown, to carry the roller 36 at the end opposite the trunnions 4S. The arm 49 is also provided with stitening web members S2 and 53 which interconnect the side members 50, and a downwardly projecting portion 54, disposed beneath the roller 36, having a socket SS adapted to pivotally receive the end of connecting rod 57 of a hydraulic piston and cylinder assembly 58. Hydraulic piston and cylinder assembly 58 isV supported on frame member il by appropriate trunnions 59; it will be evident that by actuation of cylinder and piston assembly 58, the arm e9 and the rollers 36 and 37 can be raised from their lower position shown in full lines in FIGURE 4 to the raised position shown in broken lines in FIGURE 4.

in order to provide for the accurate positioning of the rollers 36 and 37 for engagement with a mandrel rod of any given diameter within the range for which the machine is adapted, one of the side members 5G is provided with an upwardly extending projection 6i, see FIGURE 4, having a at surface 62 adapted to engage the end of an adjustable stop 63 which is threaded in a bracket 64 rigidly mounted on the supporting member 38 (see FIGURES 3 and 5). The stop 63 may take any convenient form; it is shown herein as a simple, adjustable threaded member arranged to be locked in position by an appropriate locking member 65. The stop limits the upward movement, upon actuation of cylinder 58, of arm i9 about the pivot provided by trunnions 48 Vand is adjusted so that when surface 62 engages the stop the rollers 36 and 37 are disposed in the proper position to engage and support a mandrel bar of the diameter that is then being used. The rollers are held in this raised position by the force exerted by cylinder S3.

The mandrel bar 17 is held firmly against rollers 36 and 37 by the upper roller 35. This roller is carried by a supporting arm 66, FIGURES 3 and 4, which is pivotcd as at 67 and 68 on the upwardly extending portions 70 and il of the brackets 38 and 39. The supporting arm 66 has a transversely extending central lever portion 73 to which the connecting rod 74 of the actuating cylinder and piston assembly 7S is pivotally connected as shown at 76. The cylinder and piston assembly 75 is pivotally supported by means of trunnions 77 mounted in appropriate bearing blocks carried by bracket 78, which is secured to base member 42. With this arrangement the cylinder 75 can be actuated to urge the roller 3S downwardly toward the rollers 36 and 37 and into engagement with the mandrel bar 17 so as to hold the mandrel bar firmly against the rollers 36 and 37. Actuation of the cylinder 7S in the opposite `direction raises the roller 35 to the broken line position shown in FIGURE 4 so that a shell, which has been pierced in the apparatus, can be removed readily from the apparatus by the discharge arms 29.

With this mechanism the stop 63 is set to locate the lower rollers 36 and 37 in the correct position and the cylinder 58 actuated, when the mandrel is in place, to bring the rollers up into engagement with the mandrel, the motion of the rollers being limited by the stop 63. Then the cylinder '75 is actuated to bring the upper roller 35 down into engagement with the mandrel bar, holding it firmly against the rollers 36 and 37 and restraining it against vibration as the mandrel bar rotates rapidly dur ing the piercing operation.

The lower rollers 36 and 37 are so disposed relative to each other and relative to upper roller 35 that the rollers engage any mandrel bar without regard to its size within the range of sizes which may be used in the apparatus, in arcuately spaced relation and maintain the mandrel bar and piercing point 16 centered relative to the piercing rolls 10 and 11 provided the stop 63 is properly adjusted for the size mandrel bar then in use. Thus with stop 63 properly set for the size mandrel bar in use and surface 61 in engagement therewith the lower rollers are positioned so that when the upper roller bears upon the mandrel bar and holds it firmly against the lower rollers the mandrel bar and piercing point are automatically centered and held in the proper position during the piercing operation so that the billet is pierced with a high degree of accuracy.

In operation, controls for the cylinders 58 and 75 are arranged so that the uid pressure in the cylinders is released and the cylinders retracted to raise the upper roller 35 and lower the lower rollers 36 and 37 away from the mandrel immediately before the tube or shell that is being pierced reaches the mandrel bar steadier 31 or 32 as the case may be. To this end I provide each mandrel bar steadier with a conventional limit switch 79. Switch 79 is disposed on the feed side, top as viewed in FIGURE 3, of the steadier so that the shell engages the switch to open the rollers before it reaches the rollers and is adjustably mounted so it may be properly positioned for whatever size shell is being produced. However, according to the present invention, means are provided for releasing the pressure on the rollers if the limit .switch for some reason should fail to operate.

T o this end I dispose beveled end SG of upper roller 35 nearer the direction top as viewed in FIGURE 3, from which the pierced shells or pipe advance through the mill than the corresponding ends of the lower rollers 36 and 37. Thus, should the limit switch 79 fail, the advancing shell first contacts end Si? of roller 35 and the means for releasing the pressure on the rollers is adapted to respond to this contact. This is accomplished by the hydraulic and electrical circuits shown diagrammatically in FIG- URE 7.

A preferred form of control circuit may embody a main control valve 82 which is connected to a source of tluid under pressure by a hydraulic line 83 and to a sump or the like by a hydraulic exhaust line S4 and hydraulic control lines S5 and S6. ln one position of the valve 82, the pressure line 83 is connected to line S5 and the exhaust line S4 to line 86; and in the other position of the valve 82, the connections are reversed so that presvsure line 83 is connected to line 86, and exhaust line 84 to line 85. The valve is operated by solenoids or the lilre through the control S8, which may be arranged for either manual or automatic operation. These elements may all be of well-known construction.

Hydraulic line 85 is divided intoa branch S9 leading to cylinder 75 for operating the upper roller 35 and a branch 9) leading to cylinder 5S for operating the lower rollers 36 and 37. Line 90 includes a pilot check valve 9i and a speed control valve 92 which limits the rate of iiow of hydraulic iiuid through the conduit 90 to a predetermined maximum so that the cylinder 5S will not move the rollers 36 and 37 upwardly too rapidly. When valve 82 is positioned so that line 83 is connected to line S5', pressure is applied to line 9d and cylinder 5S moves the arm 49 and rollers 36 and 37 upwardly until the projection 6l engages the stop 63. The pilot check valve 9i prevents return how of 'duid and thus holds the arm 49 in the raised position. While the piston of the cylinder 58 is being raised, the hydraulic fluid above the piston ows freely through the speed control valve 94 to the conduit S6, and thence through the main valve and conduit S4 to the sump.

Line S9 includes a pressure regulating valve 95, a speed control valve 96, which functions in the same manner as the speed control valve 92, and a pressure switch 97. When line 33 is connected to line 85, pressure is also applied to line S9 and cylinder 75 is raised to pivot the arm 66 about the pivots 67 and 63 and move the upper roller 35 downwardly into engagement with the mandrel bar, which has previously been positioned on the rollers 36 and 37. The date at which roller 35 is lowered is controlled by the speed control valve 96, and the pressure with which it engages the mandrel bar is controlled by the pressure regulating valve 95. The hydraulic Huid above the ,piston in cylinder 75 iiows freely through the speed control valve S to conduit 36 and thence through the main valve and to the sump through conduit 84.

When the position of the main valve is changed and the connections reversed so that line 83 is connected to line 86, pressure is supplied through conduit S6 and the speed control valves 94 and 98 to the upper portions of the cylinders 58 and 75, respectively. The speed of operation is then controlled by the speed control valves 94 and 93 and the fluid can iiow freely through speed control valves 92 and 96. Increase in pressure in the line 86 'releases the pilot check valve 91, the pressure inline 86 acting on the valve through line 1th). Upon release of the check valve 9i, `duid from the lower part of the cylinder 5d can ow back through the conduit 9i) and conduit 5 to the exhaust line 34. Similarly, fluid from the bottom part of the cylinder Hows through the conduit $9, conduit S5 and main valve to the exhaust line S4.

In the event that the pressure exerted on the cylinder 75 becomes excessive, while the upper roller 35 is in the downwardly position as a result, for example, of a tube, while being pierced, engaging the tapered portion Sti of the roller 35 and thus forcing the roller upwardly against the action of the cylinder 75, the resulting increase in pressure in the line 89 actuates pressure switch 97, and, by appropriate electrical connections, causes control 88 to immediately actuate main valve 82; to position it to release the pressure in the lower part of the cylinders 58 and 75 and to supply pressure to the upper parts of the cylinders 53 and 75 (i.e., connecting lines 33 and 86 and 84 and S5, respectively), thereby immediately retracting the rollers 35, 36 and 37 and preventing damage from occurring in the apparatus. In general, however, this feature is primarily a safety device, the control preferably being actuated by appropriate limit switches to release the rollers 35, 36 and 37 from engagement with the mandrel just before the advancing end of the tube or shell reaches the beveled end Si? of the roller 35.

In operation, the mandrel bar 17 is advanced by means of the carriage 2t? to the working position shown in FIG- URE 1. Then the valve .82 is actuated by means of the control S8 to close the rollers 35, 36 and 37 onto the mandrel, the rollers 36 and 37 being located in the desired position by the stop 63 and the roller 35 holding the mandrel iirmly against the rollers 36 and 37. While the mandrel is being advanced, it is supported by the rollers 24 which are retracted after the mandrel bar steadiers have been engaged with the mandrel bar. The piercing operation is then carried out; and as the pierced tube or shell approaches the mandrel bar steadier 3l, limit switch 79 opens the rollers, disengaging them from the mandrel bar so that the shell can pass along the mandrel bar without coming in contact with the rollers of the steadier 3l. Then as the piercing operation progresses, the mandrel bar steadier 32 is caused to open by appropriate limit switches as the end of the shell approaches that unit. When the piercing operation is completed, the mandrel bar steadiers are already in open position with the rollers disengaged from the mandrel bar so that it is only necessary to retract the mandrel bar and actuate the discharge arms 29 to remove the pierced tube from kthe apparatus, whereupon the apparatus is ready for another cycle of operation.

From the foregoing description of a preferred form of the invention, it will be evident that I have provided a simple and sturdy mandrel bar steadier in which relatively large rollers can be employed because only three are re- .quired to support the mandrel bar and in which adjustments for a wide range of sizes of mandrel bar can be made without requiring changes in the size of the rollers. The actuating linkage embodies only two levers to support the rollers and two cylinders to move the rollers into and out of their proper position. Thus, the mechanism is simple, sturdy and rigid. The lower rollers are brought into position against a ixed stop kand lock hydraulically in the ydesired position, while the upper roller holds the mandrel iirrnly against the two lower rollers. Because of this arrangement, the bar is effectively held against vibration and located in the proper position with only one adjustment being necessary' for various sizes of bars. The duid pressure switch prevents damage occurring to the bar steadiers in the event of failure of the limit switches to open the respective steadiers before the pierced tube shell reaches them, and the steadiers are so constructed that the ysteadiers themselves can be removed from the outlet table `simply V,by disconnecting the .bolts d3 and 46S and lifting the trunnions 59 and 77 out of their bearings Without disturbing the remainder of the outlet table in any way. Thus, the invention provides an effective, sturdy and simple mandrel har steadier having improved operating characteristics and long life.

Those skilled in the art will appreciate that various changes and modifications can be made in the invention without departing from the spirit and scope thereof. The essential features of the invention are deiined in the appended claims.

l claim:

1. A mandrel bar steadier for a piercing mill outlet table along which pierced pipe advances, said mandrel bar steadier being adapted to engage and support a longitudinally extending mandrel bar and comprising a base, a lower rollers supporting arm having an end pivotally mounted on said base at one side thereof relative to said outlet table, said lower rollers supporting arm extending transversely of said outlet table and curving upwardly remote from said pivotally mounted end, said mandrel bar steadier also comprising a pair of longitudinally extending lower rollers carried by said lower rollers supporting arm and spaced apart by said curved portion thereof, a lower rollers supporting arm hydraulic operating cylinder pivotally secured to said base and having a piston with a connecting rod pivotally secured to said lower rollers supporting arm, adjustable co-acting stop and stop engaging means carried by said base and said lower rollers supporting arm, an upper roller supporting arm pivotally supported on said base and extending transversely of said outlet table and supporting a longitudinally extending upper roller, an upper roller supporting arm operating cylinder pivotally secured to said base and having a piston with a connecting rod pivotally secured to said upper roller supporting arm, said rollers being positioned by said cylinders respectively and having a closed position adapted to engage said mandrel bar and an open position out of engagement with said mandrel bar, said rollers having ends and being arcuately spaced about said mandrel bar when in said closed position, said lower rollers supporting arm engaging said stop when said rollers are in said closed position, and means to actuate said cylinders to open said rollers in response to engagement of said mandrel bar steadier by said pipe as it advances along said table, said last named means including a pressure switch responsive to an increase in pressure in said upper roller operating cylinder to actuate said cylinders to open said rollers, and a bevel on one said end of said upper roller, said beveled end being longitudinally nearer the direction from which said pipe advances along said outlet table than the other said ends of said lower rollers.

2. A mandrel bar steadier for a piercing mill outlet table along which pierced pipe advances, said mandrel bar steadier being adapted to engage longitudinally extending mandrel bars of varying diameter and support them with their respective axes coinciding with a predetermined centerline, said mandrel bar steadier comprising a base, a lower rollers supporting arm having an end pivotally mounted on said base at one side thereof relative to said outlet table for limited rotation about an axis, said lower rollers supporting arm extending transversely of said outlet table and having an upwardy curved portion remote from said pivotally mounted end, a pair of longitudinally extending, transversely spaced lower rollers carried by said lower rollers supporting arm, said lower rollers having axes in lixed relation relative to said lower rollers supporting arm and spaced apart by said upwardly curved portion thereof, whereby said rollers are adapted to engage and support mandrel bars of different predetermined diameters to maintain their respective axes on said centerline, adjustable co-acting stop and stop engaging means carried by said base and said lower rollers supporting arm, an upper roller supportingarm pivot- 8 ally supported on said base and extending transversely of said outlet table, a longitudinally extending upper roller supported on said upper roller supporting arm, and means to position said upper and lower supporting arms, said rollers having a closed position adapted to engage a man# drel bar of selectively predetermined diameter when said -stop and stop engaging means are engaged and an open position out of engagement with said mandrel bar.

3. A mandrel bar steadier for a piercing mill outlet table along which pierced pipe advances, said mandrel bar steadier being adapted to engage and support a longitudinally extending mandrel bar and comprising a base, first and second supporting arms pivotally secured to said base and extending transversely of said outlet table, at least one roller carried by each of said supporting arms, said rollers having a closed position in engagement with said mandrel bar and an open position out of engagement with said mandrel bar, a hydraulic operating cylinder pivotally secured toeach said supporting arm and being operable to actuate said arms, respectively, to move said rollers into and out of said closed position, means to selectively actuate said cylinders to close said rollers and means for automatically actuating said cylinders to open said rollers in response to the advance of said pipe along said outlet table, said last named means including a pressure switch responsive to a predetermined increase in pressure in one said cylinder to actuate said cylinders to open said rollers, and one said roller on said Supporting arm operated by said one cylinder being beveled, said beveled end being longitudinally nearer the direction from which the pipe advances along said outlet table than the other ends of said rollers, said beveled end being engageable by said pipe advancing along said table and engagement between said pipe and said beveled end causing said predetermined increase in pressure in said one cylinder.

4. A mandrel bar steadier for a piercing mill outlet table along which pierced pipe advances, said mandrel bar steadier being adapted to engage longitudinally extending mandrel bars of varying diameter and support them with their respective axes coinciding with a predetermined centerline, said mandrel bar steadier comprising a base, a first roller supporting arm extending transversely of said outlet table and having an end pivotally mounted on said base for rotation about a longitudinally extending axis, a pair of longitudinally extending, transversely spaced rollers carried by said first roller supporting arm, said rollers having axes in iixed relation relative to each other and to said first roller supporting arm and being spaced apart by being disposed at different radial distances from said ii-rst roller supporting arm axis on angularly spaced radii thereof, said rollers having cylindrical surfaces which are equidistant from said centerline while said irst roller supporting arm is rotated through a limited angle about said axis, `whereby said rollers are adapted to engage mandrel bars of different predetermined diam eters to maintain their respective axes on said centerline, a second roller supporting arm pivotally supported on said base and extending transversely of said outlet table, a longitudinally extending roller supported on said second roller supporting arm and adapted to engage the mandrel bar, and means to actuate said iirst and second supporting arms to move said rollers into and out of engagement with a said mandrel bar.

5. A mandrel bar steadier for a piercing mill outlet table along which pierced pipe advances, said mandrel Yhar steadier being adapted to engage and support a longitudinally extending mandrel bar and comprising a base, lirst and second supporting arms pivotally secured to said base and extending transversely of said outlet table, at least one roller carried by each of said supporting arms, said rollers having a closed position in engagement with said mandrel bar and an open position out of engagement with said mandrel bar, a hydraulic operating cylinder pivotally secured to each said supporting arm and being operable to actuate said arms, respectively, to move said rollers into and out of said closed position, means to selectively actuate said cylinders to close said rollers and means for automatically actuating said cylinders to open said rollers in response to the advance of said pipe along said outlet table, said automatically actuating means including a limit switch supported in operable relation with said advancing pipe and nearer the direction from which said pipe advances than said rollers and operable by the advance of said pipe to actuate said cylinders to open said rollers, said automatically actuating means also including a pressure' switch responsive to a predetermined increase in pressure in one said cylinder to actuate said cylinders to open said rollers, and means to actuate said pressure switch to open said rollers if said limit switch fails to open said rollers, said last married means comprising providing one said roller on said supporting arm operated by said one cylinder with a beveled end, said beveled end being longitudinally nearer the direction from which the pipe advances along said outlet table than the other ends of said rollers, said beveled end being engageable by said pipe advancing along said table, when said rollers are closed, and engagement between said pipe and said beveled end causing said predetermined increase in pressure in said one cylinder.

References Cited in the tile of this patent UNITED STATES Parleurs 844,349 Hale Feb.' 19, 1907 2,104,117 Findlater Jan. 4, 1938 2,156,218 Assel Apr. 25, 1939 2,205,632 Schwarz et al June 25, 1940 2,263,744 Smith Nov. 25, 1941 2,306,827 Mohan Dec. 29, 1942 2,686,444 Reichl Aug. 17, 1954 

